The investigators plan to identify, using a predominantly chemical approach, the putative, primary, afferent sensory transmitter or transmitters and their associated biochemical systems of the lateral-line hair cells of Xenopus laevis (the African clawed frog) and of the inner-ear hair cells of the guinea pig. Nontransmitter materials that are released into perilymph during exposure of guinea pigs to noise at high levels will also be identified. Major techniques include: (1) high-performance liquid chromatography with fluorescence detection of ortho-phthaldialdehyde/2-mercaptoethanol adducts of primary amines for the analysis of perilymph, (2) one- and two-dimensional polyacrylamide-gel electrophoresis for detection of proteins specific to hair-cell fractions, and (3) radioactive receptor binding assays for the determination of neurotransmitter-binding sites of the lateral-line sensory epithelium.